Thanks to Mwlhiore I spotted that my usb stick contents were far too low to be a full XP program in spite of it being formatted by usb_multiboot_10. So I've run that utility again using the full XP disc and no compression. The Aspire One is loading from the stick but now it gives the error: "Line 7594 of the INF file \txtsetup.sif is invalid. Setup cannot continue." In an effort to correct this, I've deleted that file and substituted the one from the original disc, but the error still halts the setup. I can't believe the time and trouble this XP installation is causing - other users seem to get no problems. Any further help would be appreciated.